<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>闭包</title>
</head>

<body>
    <script>
        function foo() {
            var a = 2;
            function baz() {
                console.log(a);//2
            }
            bar(baz);
        }

        function bar(fn) {
            fn();
        }

        foo();

        function wait(message) {
            setTimeout(() => {
                console.log(message);
            }, 1000);
        }

        wait('hello, world!');
    </script>
</body>

</html>